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Updated: Oct 11, 2025
An Electroporation Method to Transform Rickettsia spp. with a Fluorescent Protein-Expressing Shuttle Vector in Tick Cell Lines
Published on: October 11, 2022
Molecular identification of Rickettsia spp. in chigger mites in Taiwan
Chi-Chien Kuo1, Pei-Lung Lee2, Hsi-Chieh Wang2
1Department of Life Science, National Taiwan Normal University, Taipei, Taiwan.
Abstract:
The genus Rickettsia is the causative agent of several rickettsial diseases that are primarily transmitted by hard ticks. The occurrence of Rickettsia in chigger mites, which are vectors of scrub typhus in the western Pacific region, has been infrequently investigated. We identified Rickettsia spp. in chiggers collected from small mammals in six counties of Taiwan. Moreover, by capitalising on parallel Rickettsia detections on small mammals and their infested ticks and fleas, we were able to identify Rickettsia spp. that suggested more intimate associations with chigger mites. Rickettsia detection rates in 318 pools of chiggers were 21.7% and 22.3% when based on the ompB and gltA gene, respectively. Overall, we identified six (based on the ompB gene) and eight (gltA gene) Rickettsia species. Approximately half of the sequenced species were most similar to Rickettsia sp. clone MB74-1 (ompB gene) and Rickettsia sp. TwKM02 (gltA gene). Furthermore, both species were either infrequently or never identified in small mammals, ticks and fleas, which suggests that chigger mites might be the primary host of both rickettsiae. Whether both species are pathogenic to humans remains to be studied. They may also be microbial endosymbionts of chigger mites, with their potential effects on the pathogenicity of the aetiologic agent of scrub typhus deserving further investigations.
Insights
Rickettsia bacteria were found in Taiwan chigger mites, suggesting these mites may be primary hosts for previously unknown species. Further research is needed to determine their pathogenicity and role in scrub typhus transmission.
Area of Science:
- Microbiology
- Vector-borne diseases
- Parasitology
Background:
- Rickettsia bacteria cause various diseases, typically transmitted by hard ticks.
- Chigger mites are vectors of scrub typhus, but Rickettsia presence in them is understudied.
Purpose of the Study:
- To investigate the presence and diversity of Rickettsia species in chigger mites from Taiwan.
- To explore potential novel host associations for Rickettsia.
Main Methods:
- Chigger mites were collected from small mammals across six counties in Taiwan.
- Rickettsia DNA was detected using ompB and gltA genes.
- Sequencing identified Rickettsia species and their similarity to known strains.
Main Results:
- Rickettsia spp. were detected in 21.7% (ompB) and 22.3% (gltA) of chigger pools.
- Six to eight Rickettsia species were identified, with some novel strains.
- Identified Rickettsia species were rarely found in co-infesting mammals, ticks, or fleas.
Conclusions:
- Chigger mites in Taiwan harbor diverse Rickettsia species, potentially serving as primary hosts.
- Two novel Rickettsia species may have intimate associations with chigger mites.
- The pathogenicity and role of these Rickettsia in scrub typhus require further investigation.
